Expression of E6 and E7 papillomavirus oncogenes in the outer root sheath of hair follicles extends the growth phase and bypasses resting at telogen

Hair follicle growth cycle proceeds through a series of stages in which str ict control of cell proliferation, differentiation, and cell death occurs. Transgenic mice expressing human papillomavirus type 16 E6/E7 papillomaviru s oncogenes in the outer root sheath (ORS) display a fur phenotype characte rized by lower hair density and the ability to regenerate hair much faster than wild-type mice. Regenerating hair follicles of transgenic mice show a longer growth phase (anagen), and although bulb regression (catagen) occurs , rest at telogen was not observed. No abnormalities were detected during t he first cycle of hair follicle growth, but by the second cycle, initiation of catagen was delayed, and rest at telogen was again not attained, even i n the presence of estradiol, a telogen resting signal. In conclusion, expre ssion of E6/E7 in the ORS delays entrance to catagen and makes cells of the ORS insensitive to telogen resting signals bearing to a continuous hair fo llicle cycling in transgenic mice.